Method and apparatus for repair of polyolefin pipes and structures

ABSTRACT

A method of repairing a polyolefin structure at a damaged area thereof containing applying a filler material as necessary to fill the damaged area, overlaying the filled damaged area with a transitional film having a first side adapted to bond to polyolefins, bonding the transitional film to the polyolefin structure, and applying a reinforcement system over the transitional film. The bonding of the transitional film to the polyolefin structure comprises applying heat to the transitional film. 
     A repair system for repairing a polyolefin structure containing optionally a filler material on the polyolefin structure, a transitional film applied over and bonded to the polyolefin structure having a first side adapted to bond to polyolefins, and a reinforcement system, applied over the transitional film. The reinforcement system contains a fiber-reinforced polyurethane system bonded to the second side of the transitional film.

RELATED APPLICATIONS

This application is a Continuation of co-pending U.S. application Ser.No. 14/668,096, entitled, “Method and Apparatus for Repair of PolyolefinPipes and Structures” filed on Mar. 25, 2015, which is hereinincorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates generally to polyolefin pipes and otherstructures, and more particularly relates to a method and apparatus forrepairing and/or joining polyolefin pipes and other structures.

BACKGROUND OF THE INVENTION

Polyolefin materials include the following: thermoplastic polyolefins:polyethylene (PE), polypropylene (PP), polymethylpentene (PMP),polybutene-1 (PB-1); Polyolefin elastomers (POE): polyisobutylene (PIB),ethylene propylene rubber (EPR), ethylene propylene diene monomer(M-class) rubber (EPDM rubber). Such materials, especially in a tubularconfiguration (i.e., pipes), are utilized to deliver or convey anassortment of media that may have corrosive chemical properties. PE andPP pipe is commonly used by gas utility companies, for example. Suchpipes themselves may be deployed in environments that also subject theexterior of the pipe to corrosive or otherwise physically or chemicallydamaging conditions. Polyolefins are also materials from which variousother types of structures, such as holding tanks, pressure vessels andthe like, which may be deployed in harsh environments.

When deploying polyolefin pipe in a particular application, it is ofcourse frequently necessary to join two sections of pipe togetherend-to-end. One method of accomplishing this is by welding the pipesections together. In a common technique known as butt fusion, the twopipe sections are heated by a welding plate in the form of a heated diskto cause the ends of the pipes to become molten. The welding plate isthen removed and the pipe sections are pressed together with somepredetermined force for some predetermined duration of time, dependingupon wall thickness and pipe diameter. The result is a weld joint thattypically has a circumferential bead cap. There are known potentialproblems with such weld joints, due to stress differentials and the likethat may exist in the heat-affected zone. Weld joints are susceptible tocracking over time, either due to external forces, such as soil movementor physical impact, or due to the material becoming brittle over time.

There are also various types of field connections that may be made topolyolefin pipe. These include couplings such as tees, elbows, reducers,and so on. Field connections typically employ some form of crimpingforce to squeeze the joints together. This crimping process is known tointroduce micro-cracks in the pipe material. These micro-cracks can growover time, due to cyclic pressures, exposure to temperature swings,material embrittlement, and so on, leading to failure or leaks.

Persons of ordinary skill in the art will appreciate that polyolefinsare materials that by their very nature are difficult to bond to, due totheir molecular density and low surface energy. This prevents mostsimple methods of bonding most types of materials to a polyolefinsurface from being entirely effective. Consequently, there hasheretofore been little that could be done to repair polyolefinstructures that have become degraded by mechanisms such as describedabove. Pipes may exhibit mechanical damage, including the growth ofmicro-cracks that can be induced from crimp connections. Of course, thisis undesirable where such defects could allow for leaking, posingdangers to individuals or the environment.

SUMMARY OF THE INVENTION

In view of the foregoing and other considerations, the present inventionis directed to a method and apparatus for repairing polyolefinstructures, particularly (but not exclusively) PE or PP pipe. In oneembodiment of the invention, a damaged area of a polyolefin pipe hasfiller material applied thereto as necessary to fill cracks, voids, orother degradation of the pipe. Following application of a fillermaterial, a transitional film is applied over the area being repaired.The transitional film has a first side that is adapted to bond topolyolefins. The bonding process may involve application of heat and/orcompressive force. After the transitional film is applied and bonded, areinforcement system, such as a fiber-reinforced polyurethaneapplication, is applied over the repair area to complete the repairprocess.

In another embodiment of the invention, a butt weld joint is repaired orreinforced. In some cases, it may be necessary to prepare the joint bysmoothing or eliminating the bead cap formed during the welding process.In this embodiment, no filler material may be necessary. Thetransitional film as described above is applied over the joint andbonded to the joined segments of pipe. Thereafter, a reinforcementsystem is applied over the transitional film to complete the repair orpreventative reinforcement of the weld joint.

In another embodiment of the invention, a crimped area, such as at afield connection, is repaired or reinforced, in a manner similar to thatdescribed above for repairing or reinforcing a butt weld.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is best understood with reference to the followingdetailed description of embodiments of the invention when read inconjunction with the attached drawings, in which like numerals refer tolike elements, and in which:

FIG. 1 is a side, longitudinal cross-sectional view of a length of pipeto be repaired in accordance with one embodiment of the invention;

FIG. 2 is a side, longitudinal cross-sectional view of the pipe fromFIG. 1 having a filler material applied in a damaged area thereof;

FIG. 3 is a side, longitudinal cross-sectional view of the pipe fromFIG. 2 having a transitional film applied thereover;

FIG. 4 is a side, longitudinal, cross-sectional view of the pipe fromFIG. 3 having a reinforcement system applied over the repair areaincluding the transitional film;

FIG. 5 is a side, longitudinal, cross-sectional view of two sections ofpipe aligned end-to-end in preparation for a joining operation inaccordance with one embodiment of the invention;

FIG. 6 is a side, longitudinal, cross-sectional view of the two sectionsof pipe from FIG. 5 with a transitional film applied over the jointarea;

FIG. 7 is a side, longitudinal, cross-sectional view of the two sectionsof pipe from FIG. 5 with a reinforcement system applied over thetransitional film;

FIG. 8 is a side, longitudinal, cross-sectional view of two sections ofpipe having been welded together using a conventional butt fusiontechnique;

FIG. 9 is a side, longitudinal, cross-sectional view of the two weldedsections of pipe from FIG. 8 with the joint reinforced in accordancewith one embodiment of the invention;

FIG. 10 is a flow diagram illustrating the steps of repairing a tubularmember in accordance with one embodiment of the invention; and

FIG. 11 is a flow diagram illustrating the steps of repairing anon-tubular member in accordance with another embodiment of theinvention.

FIG. 12 is a side, longitudinal, cross-sectional view of a holding tankwith a reinforcement system applied over the transitional film.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

In the disclosure that follows, in the interest of clarity, not allfeatures of actual implementations are described. It will of course beappreciated that in the development of any such actual implementation,as in any such project, numerous engineering and technical decisionsmust be made to achieve the developers' specific goals and subgoals(e.g., compliance with system and technical constraints), which willvary from one implementation to another. Moreover, attention willnecessarily be paid to proper engineering practices for the environmentin question. It will be appreciated that such development efforts mightbe complex and time-consuming, outside the knowledge base of typicallaymen, but would nevertheless be a routine undertaking for those ofordinary skill in the relevant fields.

Referring to FIG. 1, there is shown a longitudinal, cross-sectional viewof a section of polyolefin pipe (e.g., PE or PP pipe) identified withreference numeral 10. As shown in FIG. 1, pipe 10 has a damaged area 12at which pipe 10 has been degraded. Although the embodiment of FIG. 1comprises a pipe, those of ordinary skill in the art having the benefitof the present disclosure will appreciate that the invention may bepracticed in connection with other types of PE structures.

FIG. 2 illustrates a first step in a repair method in accordance with anexemplary embodiment of the invention, wherein a filler material 14 isapplied over the damaged area 12 as necessary to fill the damaged area12. In one embodiment, the filler material 14 may be a polyester, epoxy,vinyl ester, polyurethane, thermoplastic material, rubber compound, oracrylic, such as a methylacrylate or thermoplastic material.

Once the filler material has been applied and cured or otherwisehardened, a next step in accordance with the disclosed embodiment of theinvention is to overlay a transitional film 16 over the section of pipebeing repaired. This is shown in FIG. 3. In a presently preferredembodiment of the invention, the transitional film 16 comprises NolaxS22.2202, a co-extruded multi-layer adhesive film commercially availablefrom Nolax AG, a member of the Colla no Group headquartered in SempachStation, Switzerland. See www.nolax.com.

A preferred attribute of the transitional film 16 is that it is adaptedon one side thereof to bond effectively with polyolefinic materials,such as PE, EVA, EPOM, and PP and adapted on the opposite side thereofto bond to PVC, polyurethane, ABS, PC, PA, etc.

In an exemplary embodiment, the transitional film is wrapped around thelength of pipe 10 being repaired. Those of ordinary skill in the artwill recognize that the bonding of film 16 to pipe 10 must be activated.Typically, this is accomplished by means of application of heat andcompressive force. One method of accomplishing this is through the useof heat-activated shrink tape (not shown in the Figures), such as 220R4″ 20% shrink release coated roll commercially available from DunstonInc., headquartered in Charlotte, N.C., United States. Seewww.shrinktape.com.

Once film 16 has been bonded to pipe 10 over the area being repaired, anouter reinforcement system 18 is applied over the repair area, as shownin FIG. 4. Note that the heat shrink tape or other means for activatingthe bond of the film 14 to pipe 10 is preferably removed prior toapplication of the outer reinforcement system 18 and hence is not shownin FIG. 4. In one preferred embodiment of the invention, the outerreinforcement system 18 comprises A+ Wrap™, a high-strength wrapcomprised of a fiberglass reinforced substrate factory impregnated withmoisture-cured polyurethane. A+ Wrap™ is commercially available fromPipe Wrap, Inc., Houston, Tex. Seehttp:Uwww.piperepair.net/products/structural-repair/a-wrap/, herebyincorporated by reference herein in its entirety. In another embodiment,the outer reinforcement system 18 comprises a fiber-reinforced epoxysystem, such as FormaShield™, which is also commercially available fromPipe Wrap, Inc. Seehttp://www.piperepair.net/products/structural/repair/formashield/,hereby incorporated by reference herein in its entirety.

In addition to providing a means of effectuating structural repair ofpolyolefin structures such as PE pipes, as described above withreference to FIGS. 1-4, it is contemplated that the present inventionmay be employed to create a joint between two sections of pipe,circumventing the need for a conventional butt fusion operation. This isshown in FIGS. 5-7.

In particular, in FIG. 5, there is shown a longitudinal, cross-sectionalview of two sections of pipe designated with reference numerals 20 and22. Pipe sections 20 and 22 are oriented end-to-end in preparation ofthe creation of a joint therebetween.

FIG. 6 shows the respective pipe sections 20 and 22 from FIG. 5 with atransitional film layer 24 bonded over the joint area. As in thepreviously described embodiment, transitional film layer 24 is adaptedon one side to bond to polyolefins, and the bond may be activated byapplying heat and compressive force.

FIG. 7 shows the respective pipe sections 20 and 22 with a reinforcementsystem 26 applied over and bonded pipes 20 and 22 in the area oftransitional film 24. The aforementioned A+ Wrap™ or Formashield™products are contemplated to be suitable reinforcement systems 26 forthe purposes of the present invention.

It is further contemplated that the present invention may be employed asa preventative measure to strengthen the integrity of a conventionalbutt fusion joint between two sections of pipe. FIG. 8 shows twosections of polyolefin pipe 28 and 30 having been welded together usinga conventional butt fusion technique. As previously noted such atechnique commonly results in the formation of a bead cap 32 around thecircumference of the weld joint.

FIG. 9 shows the sections of pipe 28 and 30 with the weld jointtherebetween 5 reinforced in accordance with one embodiment of theinvention. From FIG. 9, it is evident that the bead cap 32 is preferablyremoved prior to application and bonding of a transitional film 32 and areinforcement system 34.

Turning to FIG. 10, there is shown a flow diagram illustrating a repairmethodology in accordance with one embodiment of the invention. Inparticular, the process depicted in FIG. 10 is believed to be thepreferable means of repairing tubular members, such as pipes.

As shown in FIG. 10, the first step 40 is to clean the repair area, forexample, with an appropriate solvent, to assure optimal bonding duringthe repair process.

As described above, the next step 42 is to apply filler material asnecessary to provide a relatively smooth repair surface. This step 42may or may not be necessary depending upon the nature of the damagebeing repaired. As noted above, suitable filler materials may be apolyester, epoxy, vinyl ester, polyurethane, thermoplastic material,rubber compound, or acrylic, such as a methylacrylate or thermoplasticmaterial.

The next step 44 is to apply the bi-material coextruded transitionalfilm to the repair area. In one embodiment, bonding of the transitionalfilm to the repair area is accomplished by applying heat, such as with aheat gun or the like, as represented by block 46.

Next, in block 48, a reinforcement system is applied over the repairarea. The aforementioned A+ Wrap™ or FormaShield™ systems are candidatesfor the reinforcement system.

Next, in block 50, compressive force is applied to the repair area. Asnoted above, one manner of accomplishing this is through the use ofheat-shrinking tape that is wrapped around the tubular member beingrepaired and then applying heat, such as with a heat gun, to cause thetape wrap to constrict or compress around the tubular member and therepair area.

As noted in block 52, the reinforcement system is allowed to cure, atwhich time the means of applying compressive force (e.g., theheat-shrink tape) may be removed.

Turning now to FIG. 11, there is shown an embodiment of the inventionwhich may be advantageously employed for the repair of non-tubularpolyolefin members. The process begins with block 56, wherein the repairsurface is prepared by cleaning, with appropriate solvent(s). As in theprevious embodiments, a filler material may or may not be applied, asrepresented by block 58 in FIG. 11.

In block 60, the hi-material, co-extruded transitional film is applied,as hereinbefore described. Heat is the preferred method of bonding thetransitional film to the repair area, as reflected by block 52.Thereafter, a reinforcement system as described above is applied.

In the embodiment of FIG. 11, a next step, in block 66, is to apply arelease film over the reinforcement system. In a preferred embodiment,the release film is a silicone-treated PE sheet that is perforated.Following application of the release film, a bleeder cloth material isapplied over the repair area, as represented by block 68. In oneembodiment, the bleeder cloth material is a non-woven polyester materialadapted to absorb excess resin out of the reinforcement system duringthe cure process.

A vacuum bag pressure system is employed to exert compression force onthe repair area as the reinforcement system is curing. In block 70 ofFIG. 11, a vacuum bag is sealed around the repair area. In oneembodiment, a zinc-oxide based double-sided tape is used to create theseal of the vacuum bag, which may be a high-density PE film, forexample.

In block 72, vacuum pressure is applied to compress the vacuum bagagainst the repair area. This compression force is maintained for aslong as it takes for the reinforcement system to cure, typically two tofour hours.

From the foregoing detailed description, it will be apparent to those ofordinary skill in the art that a method and apparatus (system) forrepair polyolefin structures such as PE or PP pipes as well asnon-tubular structures, such as holding tanks and the like, has beendisclosed. FIG. 12 illustrates a side, longitudinal, cross-sectionalview of a holding tank 200 with a reinforcement system 18 applied overthe transitional film 16 which is over filler material 14 which fills adamaged area. Although specific implementation details have beenprovided herein, this has been done solely for the purposes ofillustrating generally the scope of the invention, which is defined inthe claims which follow. It is to be understood that varioussubstitutions, alterations, and/or modifications may be made to thedisclosed embodiment without departing from the actual scope of theinvention.

The invention claimed is:
 1. A method of repairing a polyolefinstructure at a damaged area thereof, comprising: (a) applying a fillermaterial as necessary to fill the damaged area; (b) overlaying thefilled damaged area with a transitional film having a first side adaptedto bond to polyolefins; (c) bonding the transitional film to thepolyolefin structure, wherein the bonding of the transitional film tothe polyolefin structure comprises applying heat to the transitionalfilm; (d) applying a reinforcement system over the transitional film. 2.The method of claim 1, wherein the polyolefin structure is a non-tubularstructure.
 3. A method in accordance with claim 1, wherein the step (d)of applying a reinforcement system over the transitional film comprisesapplying a fiber-reinforced epoxy system which bonds to a second side ofthe transitional film.
 4. A method of repairing a polyolefin structureat a damaged area thereof, comprising: (a) applying a filler material asnecessary to fill the damaged area; (b) overlaying the filled damagedarea with a transitional film having a first side adapted to bond topolyolefins; (c) bonding the transitional film to the polyolefinstructure; (d) applying a reinforcement system over the transitionalfilm, wherein applying a reinforcement system over the transitional filmcomprises applying a fiber-reinforced epoxy system which bonds to asecond side of the transitional film.
 5. The method of claim 4, whereinstep (d) further comprises wrapping the polyolefin structure withheat-activated shrink tape and heating the damaged area to activate abonding process of the transitional film to the polyolefin structure. 6.The method of claim 4, wherein the polyolefin structure is a non-tubularstructure.
 7. The method of claim 4, wherein the polyolefin structure isa holding tank.
 8. A method of repairing a polyolefin structure at adamaged area thereof, comprising: (a) applying a filler material asnecessary to fill the damaged area; (b) overlaying the filled damagedarea with a transitional film having a first side adapted to bond topolyolefins; (c) bonding the transitional film to the polyolefinstructure; (d) applying a reinforcement system over the transitionalfilm, wherein applying a reinforcement system over the transitional filmcomprises applying a fiber-reinforced polyurethane system which bonds toa second side of the transitional film.
 9. The method of claim 8,wherein step (d) further comprises wrapping the polyolefin structurewith heat-activated shrink tape and heating the damaged area to activatea bonding process of the transitional film to the polyolefin structure.10. The method of claim 8, wherein the polyolefin structure is anon-tubular structure.
 11. The method of claim 8, wherein the polyolefinstructure is a holding tank.
 12. A repair system for repairing apolyolefin structure, comprising: optionally a filler material on thepolyolefin structure; a transitional film applied over and bonded to thepolyolefin structure, the transitional film having a first side and asecond side, the first side adapted to bond to polyolefins, wherein thetransitional film comprises a bi-material co-extruded film; and areinforcement system, applied over the transitional film, wherein thereinforcement system comprises a fiber-reinforced polyurethane systembonded to the second side of the transitional film.
 13. A repair systemfor repairing a polyolefin structure, comprising: optionally a fillermaterial on the polyolefin structure; a transitional film applied overand bonded to the pipe, the transitional film having a first side and asecond side, the first side adapted to bond to polyolefins, wherein thetransitional film comprises a bi-material co-extruded film; and areinforcement system, applied over the transitional film, wherein thereinforcement system comprises a fiber-reinforced epoxy system bonded tothe second side of the transitional film.
 14. The method of claim 1,wherein the polyolefin structure is a holding tank.
 15. A method inaccordance with claim 1, wherein the step (d) of applying areinforcement system over the transitional film comprises applying afiber-reinforced polyurethane system which bonds to a second side of thetransitional film.